A dehumidifier may blow hot air due to a faulty condenser, dirty air filter, or refrigerant leak. A defective condenser fails to release heat efficiently, causing warm air to be emitted. A clogged air filter impedes airflow, leading to a buildup of heat inside the unit. A refrigerant leak can reduce cooling capacity, resulting in hot air being blown. These issues are commonly addressed by cleaning the filter, replacing the condenser, or replenishing the refrigerant.